1. Field of the Invention
The present invention relates to a technique concerning an electronic component that includes a capacitor and an inductor as constituents.
2. Description of the Related Art
In a radio frequency (hereinafter, RF) system such as a mobile phone or a wireless LAN, signals have to be subjected to phase-matching for satisfactory transmission among functional devices constituting the system. Accordingly, the input/output terminal of each device is generally provided with a passive element that includes a passive component such as an inductor or a capacitor, and that acts as a phase shifter that controls the phase of the signals.
There has been a constant demand for reduction in dimensions of various parts composing the RF system, driven by the increase in number of parts for achieving a higher performance. For making the system smaller in dimensions, an integrated electronic component manufactured based on a semiconductor processing technology, which includes a plurality of predetermined passive components such as an inductor, a capacitor, a resistance and a filter densely integrated on a substrate, may be employed as the passive element (phase shifter). Techniques related to the integrated electronic component are found, for example, in JP-A-H04-61264 and JP-A-2002-33239.
FIG. 21 is a fragmentary cross-sectional view showing an integrated electronic component X3 as related art for better understanding of the present invention. It should be noted that the integrated electronic component X3 was produced by the present inventors, and is not publicly known as of the priority date of the present application.
The integrated electronic component X3 includes a substrate 91, a capacitor 92, a spiral coil 93 (FIG. 21 shows a cross-section of a part of the lead wire thereof), an electrode pad 94, a wiring 95, and a protecting film 96. The capacitor 92 has a stacked structure including electrode films 92a, 92b and a dielectric film 92c. The spiral coil 93 is an inductor patterned in a flat spiral shape on the substrate 91, and includes an inner end portion 93a located at an innermost position of the spiral shape. The electrode pad 94 serves for external connection. The wiring 95 includes a first wiring portion 95a patterned on the substrate 91, a second wiring portion 95b patterned mainly on the protecting film 96, and a via 95c. The electrode film 92a of the capacitor 92 and the electrode pad 94 are electrically connected directly. A via 95c of the wiring 95 is connected to the electrode film 92b of the capacitor 92. Another via 95c of the wiring 95 is connected to the inner end portion 93a of the spiral coil 93. The protecting film 96 is disposed so as to cover the capacitor 92 and the spiral coil 93 on the substrate 91.
FIGS. 22A through 23D illustrate a manufacturing method of the integrated electronic component X3. To form the integrated electronic component X3, firstly the electrode film 92a of the capacitor 92 is patterned on the substrate 91, as shown in FIG. 21A. Referring to FIG. 21B, the dielectric film 92c is patterned on the electrode film 92a. An electroplating process is then performed to form the electrode film 92b of the capacitor 92, the spiral coil 93 (inner end portion 93a inclusive), and the first wiring portion 95a of the wiring 95, as shown in FIG. 21C. This is followed by formation of an insulating film 96′ on the substrate 91, as shown in FIG. 21D.
Proceeding to FIG. 23A, a resist pattern 97 is formed on the insulating film 96′. The resist pattern 97 is formed with an opening 97a corresponding to the pattern of the via 95c of the wiring 95, and an opening 97b corresponding to the pattern of the electrode pad 94. Then a wet etching process is performed over the insulating film 96′, utilizing the resist pattern 97 as the mask, as shown in FIG. 23B. At this stage, the protecting film 96 provided with an opening 96a for the via 95c and an opening 96b for the electrode pad 94 is formed. The resist pattern 97 is then removed, as shown in FIG. 23C. This is followed by an electroplating process for forming the via 95c, the second wiring portion 95b, and the electrode pad 94 as shown in FIG. 23D. That is how the integrated electronic component X3 is manufactured.
In the integrated electronic component X3, the protecting film 96 is required to have a sufficient thickness (that allows securing a gap of 10 μm or wider between the spiral coil 93 and the second wiring portion 95b) in order to prevent undue electromagnetic interaction between the spiral coil 93 serving as the inductor and the second wiring portion 95b located above the spiral coil 93. The thicker the protecting film 96 is, the more difficult it becomes to form the opening 96a having a small diameter R3′ in the process described referring to FIG. 23B, and hence to form the via 95c of a small diameter R3. Accordingly, making the protecting film 96 thick causes enlarging the minimum diameter R3 (shown in FIGS. 21 and 23D) which is applicable to each via 95c. In other words, the dimension of the thickness of the protecting film 96 determines the lower limit of the applicable diameter R3 of each via 95c. 
In the integrated electronic component X3, moreover, a length L5 of the electrode film 92b of the capacitor 92 shown in FIG. 21 cannot be made smaller than the diameter R3 of the via 95c connected to the electrode film 92b. Setting the length L5 of the electrode film 92b to be smaller than the diameter R3 of the via 95c would, in the process described referring to FIG. 23B, cause the opening 96b for the electrode pad 94 to reach as far as the electrode film 92a (the etching process has to be performed until the opening 96b for the electrode pad 94 reaches the electrode film 92a), and the opening 96a to reach the dielectric film 92c (or to even reach the electrode film 92a, depending on the size of the dielectric film 92c), as shown in FIG. 24A. Executing the process described referring to FIG. 23D with the opening 96a thus formed would, as shown in FIG. 24B, result in formation of the via 95c connected to the dielectric film 92c in addition to the electrode film 92b (or even to the electrode film 92a, depending on the size of the dielectric film 92c). Such via 95c would degrade the characteristic of the capacitor 92, and hence the characteristic of the integrated electronic component X3. Therefore, in the integrated electronic component X3, the electrode film 92b has to be formed with a sufficient length L5 (and a sufficient two-dimensional size) against the diameter R3 of the via 95c connected to the electrode film 92b. 
In order to reduce the static capacitance of the capacitor 92, while satisfying the requirement for reduction in dimensions of the integrated electronic component X3, for example the length L5 has to be set to be smaller thus to reduce the two-dimensional size of the electrode film 92b. Actually, however, the minimum applicable diameter R3 is restrained depending on the thickness granted to the protecting film 96, and besides the electrode film 92b has to be formed with a sufficient length L5 (and a sufficient two-dimensional size) against the diameter R3 of the via 95c connected to the electrode film 92b, as already stated. These factors impede the attempt of reducing the static capacitance of the capacitor 92, while satisfying the requirement for reduction in dimensions of the integrated electronic component X3.
In the integrated electronic component X3, further, it is not desirable to set a length L6 of the inner end portion 93a of the spiral coil 93 shown in FIG. 21 to be smaller than the diameter R3 of the via 95c connected to the inner end portion 93a. Setting the length L6 of the inner end portion 93a to be smaller than the diameter R3 of the via 95c would, in the process described referring to FIG. 23B, cause the opening 96b to reach as far as the electrode film 92a (the etching process has to be performed until the opening 96b for the electrode pad 94 reaches the electrode film 92a), and the opening 96a to reach the substrate 91, as shown in FIG. 25A. Executing the process described referring to FIG. 23D with the opening 96a thus formed would, as shown in FIG. 25B, result in formation of the via 95c having such a large volume as reaching the substrate 91. Such via 95c may incur degradation in Q value of the spiral coil 93. Therefore, in the integrated electronic component X3, the inner end portion 93a has to be formed with a sufficient length L6 (and a sufficient two-dimensional size) against the diameter R3 of the via 95c connected to the inner end portion 93a. 
In order to increase the Q value of the spiral coil 93, while satisfying the requirement for reduction in dimensions of the integrated electronic component X3, for example the length L6 has to be set to be smaller thus to reduce the two-dimensional size of the inner end portion 93a. Actually, however, the minimum applicable diameter R3 is restrained depending on the thickness granted to the protecting film 96, while it is desirable to form the inner end portion 93a with a sufficient length L6 (and a sufficient two-dimensional size) against the diameter R3 of the via 95c connected to the inner end portion 93a, as already stated. These factors impede the attempt of increasing the Q value of the spiral coil 93, while satisfying the requirement for reduction in dimensions of the integrated electronic component X3.